KR100905957B1 - Artificial silica and method of preparation thereof - Google Patents

Abstract

The present invention relates to a method for manufacturing artificial silica, and more particularly, pulverized and classify the feldspar coating, the pulverization is first pulverized to 100 to 150 mm, the second pulverized to 50 to 70 mm, 0.1 to 30 tertiary milling to mm, fourth milling to 0.1 to 3.0 mm, and fifth milling to 0.1 to 2.0 mm to carry out 74 to 85 wt% of SiO ₂ , 10 to 18 wt% of Al ₂ O ₃ , To prepare artificial silica comprising 0.1 to 1.0 wt% Fe ₂ O ₃ , 0.2 to 0.5 wt% CaO, 0.05 to 0.2 wt% MgO, K ₂ O 2 to 6 wt%, and 0.1 to 1.0 wt% Na ₂ O Regarding the manufacturing method of artificial silica, characterized in that

The artificial silica sand is manufactured using a feldspar coating as a starting material, and the Al ₂ O ₃ component is contained in a higher content than natural silica sand, so that cracks and cracks in the mold mold during the metal regeneration process work that occurs when the conventional silica sand is used. Eliminate the phenomenon

Synthetic silica, feldspar coating, crack phenomenon

Description

Manufacturing method of artificial silica sand {ARTIFICIAL SILICA AND METHOD OF PREPARATION THEREOF}

1 is a flow chart showing a manufacturing method of artificial silica sand according to an embodiment of the present invention.

Figure 2 is a particle size analysis graph of artificial silica sand of 8 to 12 mesh (No. 3).

Figure 3 is a particle size analysis graph of artificial silica sand of 12 to 18 mesh (No. 4).

Figure 4 is a particle size analysis graph of artificial silica sand of 20 to 40 mesh (No. 5).

5 is a particle size analysis graph of artificial silica sand of 40 to 70 mesh (No. 6).

Figure 6a is a micrograph showing the particle shape of the artificial silica sand obtained in Example 1.

FIG. 6B is an enlarged photograph of FIG. 6A.

7 is a micrograph showing the particle shape of Australian natural silica sand.

8 is a micrograph showing the particle shape of Vietnamese natural silica sand.

Figure 9 is a micrograph showing the particle shape of natural silica of China.

10 is a micrograph showing the particle form of jumjinsan natural silica sand.

The present invention relates to a method of manufacturing artificial silica, and more specifically, Al ₂ O ₃ component is contained in a higher content than natural silica sand and cracks and cracks of the mold mold during the casting process operation that occurs when using the conventional silica It relates to a method of manufacturing artificial silica sand that can eliminate the phenomenon.

'Silicate' refers to quartz grains rich in silicic acid (SiO ₂ ), and is divided into natural silica sand and artificial silica sand.

Natural silica contains 96 to 98% by weight of SiO ₂ component and contains a small amount of Al ₂ O ₃ and Fe ₂ O ₂ components. Such natural silica sand is formed by weathering rocks containing a lot of quartz, such as granites and granite gneiss. One of them is weathered sandstone, and the clay powder is washed away with water, and only quartz grains remain in its original place. The other is that quartz grains are swept by the river water together with clay, and only quartz is deposited in a certain place by the difference of specific gravity. It is called sedimentary silica sand.

Silica forming silica is composed of Si (46.7%) and O (53.3%), wherein quartz (Quartz), tridimite, cristobalite, etc., depending on the form of the Si and O bonding 3 There are three types.

Natural silica produced in nature is mostly a-Quartz, and is transferred to the high or low temperature form of tridimite, cristobarite and its complex form by repeated heating or cooling.

The most important use of such natural silica sand is used for the glass industry and casting industry, such as plate glass and glass products, and is widely used for other steelmaking, steelmaking, cement, sodium silicate, chemical industry filler, and refractory brick production. In addition, it is very important as a raw material of glass fiber which requires the characteristics of electrical insulation, heat retention, and cold storage.

However, because natural silica is a non-metallic mineral, even if the same purpose is used, the quality requirements of different companies are different. In particular, the physical and chemical properties vary greatly depending on the content of SiO ₂ and Al ₂ O ₃ . Therefore, it is often advantageous to continuously use raw materials from the same mine or the same area in order to maintain a constant product quality.

However, due to the lack of de-ironing and powdering technology, high-quality silica sand and special-purpose raw materials used in electronic products depend on imports.

Domestic natural silica sand is mixed with low quality Chinese products due to lack of supply due to permit collection regulations. However, Chinese products are also decreasing their exports due to growing domestic demand. The company imports and uses Australian silica sand, which is about $ 8-10 per tonne ($ 20 in China, $ 21 in Vietnam, as of 2004) compared to Chinese or Vietnamese. However, Australian imports have been decreasing since 2002 due to the Australian Government's nature protection policy.

On the other hand, in the case of the SiO ₂ component present in natural silica sand, a crystal phase transition occurs at a specific temperature, and a sudden volume change occurs in manufacturing a product. In other words, in the case of quartz, when the crystal phase transitions at 573 ° C., a volume change occurs and cracking or cracking occurs. In addition, when a crystal phase called cristobarite is present in addition to the quartz in natural silica sand, the transition of the crystal phase occurs at 200 to 270 ° C., and thus the cracking phenomenon becomes more serious. This causes cracking or cracking in the core or mold when a large amount of natural silica sand having a high content of SiO ₂ is used.

Therefore, a method of purifying and using natural silica sand has been proposed. However, the natural silica sand is used because of the difference in impurities, particle size and physical and chemical properties, the purification method is important. However, this method has a disadvantage in that the process may vary depending on the state of the gemstone and the yield is very complicated.

In addition, a method of changing physical and chemical properties by adding other components to natural silica sand is being implemented. For example, in developed countries such as Japan and the United States, artificial silica is used in which Al ₂ O ₃ is mixed with natural silica sand to control the content of Al ₂ O ₃ . However, this method is complicated by the addition of a separate Al ₂ O ₃ to the natural silica sand, the cost increases, and moreover, it is difficult to control the content of Al ₂ O ₃ components in artificial silica sand. Moreover, a problem of deterioration of physical properties occurs due to the presence of impurities contained in natural silica sand.

In addition, some industries are performing a process of manufacturing artificial silica sand by grinding the silica sand. The artificial silica obtained in this way is not round in shape, so during the process of reprocessing molten metal for use as a mold mold in a steelmaking company or foundry, the gas contained in the molten metal is not discharged smoothly. It is accompanied by a problem that a defect occurs.

Therefore, the content of Al ₂ O ₃ component in the artificial silica sand is controlled, the process is simple, and the manufacturing method of artificial silica sand is not required that the mold mold does not occur during the work of the water reproducing process.

An object of the present invention for solving the above problems is that the Al ₂ O ₃ component is contained in a higher content than natural silica sand, the artificial molding almost no cracking and cracking of the mold mold during the work of the casting process by expansion due to volume change It is to provide a silica sand manufacturing method.

In order to achieve the above object, the present invention

SiO ₂ 74-85 wt%, Al ₂ O ₃ 10-18 wt%, Fe ₂ O ₃ 0.1-1.0 wt%, CaO 0.2-0.5 wt%, MgO 0.05-0.2 wt%, K ₂ O 2-6 wt% And it provides artificial silica comprising 0.1 to 1.0% by weight of Na ₂ O.

The artificial silica sand has a spherical particle shape, has a particle size of 6 to 200 mesh, expands to a dry shrinkage rate of +0.40 to + 0.80% and expands to a plastic shrinkage rate of +1.2 to + 3.5%.

In addition, the present invention

Provided is a method for producing artificial silica sand which is prepared by grinding and classifying feldspar pottery.

The milling is first milled to 100 to 150 mm, second milled to 50 to 70 mm, third milled to 0.1 to 30 mm, fourth milled to 0.1 to 3.0 mm, and fifth ordered to 0.1 to 2.0 mm. It is carried out through the grinding process.

At this time, after the 4th grinding | pulverization, the powder of 3.0 mm or more is conveyed and repulverized.

Preferably, the first and second grinding is performed with a jaw crusher, the third grinding is performed with a cone crusher, the fourth grinding is performed with a hammer crusher, and the fifth grinding degree is a hammer crusher. Perform using

Hereinafter, the present invention will be described in more detail.

Artificial silica prepared according to the present invention has the same form as the granular form of natural silica sand, and contains a high content of Al ₂ O ₃ (alumina) component of 10 to 18% by weight. As a result, compared with natural silica sand containing 0.02 to 2.3% by weight of the conventional Al ₂ O ₃ component by using this to prevent cracking or cracking phenomenon due to the expansion of the volume change that occurs when applied to the mold mold, etc. during the working process.

The artificial silica sand 74 to 85% by weight of SiO ₂ , 10 to 18% by weight of Al ₂ O ₃ , 0.1 to 1.0% by weight of Fe ₂ O ₃ , 0.2 to 0.5% by weight of CaO, 0.05 to 0.2% by weight of MgO, K ₂ O 2 To 6 weight percent, and 0.1 to 1.0 weight percent Na ₂ O.

In general, in the case of SiO ₂ contained in natural silica sand, a crystal phase transition occurs at a specific temperature, and a sudden volume change occurs in manufacturing a product. In other words, in the case of quartz, when the crystal phase transitions at 573 ° C., a volume change occurs and cracking or cracking occurs. In addition, when a crystal phase called cristobarite is present in addition to the quartz in natural silica sand, the transition of the crystal phase occurs at 200 to 270 ° C., and thus the cracking phenomenon becomes more serious.

Artificial silica according to the present invention adjusts the SiO ₂ component to 74 to 85% by weight in the total composition. Although it is different depending on the type of steel used in the molten metal, it is melted at 1500 to 1630 ° C. When the content of the SiO ₂ component is less than 74% by weight, since the silica is melted at a temperature lower than the molten iron temperature, the content of SiO ₂ is increased. It is important to adjust beyond the range. On the contrary, when the content of SiO ₂ exceeds 85% by weight, the content of Al ₂ O _{3 in the} total composition of artificial silica decreases, making it difficult to control high thermal changes.

In particular, the artificial silica sand according to the present invention is adjusted to 10 to 18% by weight of the Al ₂ O ₃ component in the total composition. Al ₂ O ₃ is called alumina, and its melting point is about 2050 ° C. It is excellent in abrasion resistance, heat resistance, chemical resistance and corrosion resistance, and has high hardness, electrical insulation and heat transferability.

That is, Al ₂ O ₃ having the above characteristics has a strong heat resistance against sudden temperature changes and does not change volume such as shrinkage or expansion even at high thermal changes. As a result, it is used stably even at high temperature changes appearing when artificial silica sand is applied to a mold mold, etc., and SiO ₂ reduces the volume change caused by the transition of a crystal phase at a specific temperature.

In order to obtain the effects described above, in the present invention, the content of the Al ₂ O ₃ component is adjusted to 10 to 18% by weight in the total composition. If the content of the Al ₂ O ₃ component is less than the above range, the effect of inhibiting the volume change of SiO ₂ is low, so that cracking or cracking occurs in the mold mold during the work of regeneration. On the contrary, when the content of Al ₂ O ₃ exceeds the above range, adverse effects may occur by changing other components.

As such, the artificial silica sand according to the present invention in which the content of SiO ₂ and Al ₂ O ₃ is adjusted to a specific range includes Fe ₂ O ₃ , CaO, MgO, K ₂ O, and Na ₂ O as the remaining composition. They are treated as impurities by the composition contained in the raw material, and are contained in 0.1 to 1.0 wt% of Fe ₂ O ₃ , 0.2 to 0.5 wt% of CaO, 0.05 to 0.2 wt% of MgO, and 0.1 to 1.0 wt% of Na ₂ O. do. However, since the K ₂ O component is melted from 1200 ° C, its content should be controlled to 6 wt% or less, and preferably 2 to 6 wt%. However, these compositions are insignificant and do not significantly affect the physical properties of artificial silica sand according to the present invention.

Artificial silica sand according to the present invention including the above composition is present in a spherical state in the form of round particles. The spherical particle shape may increase the quality of the product when artificial silica is applied to various products, for example, a mold mold. In other words, when the grain shape of artificial silica sand has sharp edges, the surface area is lower than that of a sphere, so that the gas discharge of the molten metal is not smooth after the liquid is injected during the molten metal playing process, resulting in product defects.

Therefore, in order to produce a high quality product, it is important to have a spherical particle form, and in order to have such a particle form, a plurality of grinding processes are performed as described later, and a grinding process is performed using a hammer crusher. do.

The artificial silica has a particle size of 6 to 200 mesh (Mesh). In this case, the mesh is a unit representing the size of a hole or a particle of a sieve. In the Tyler Standard Sieve, a mesh is expressed as the number of scales within 1 inch. The larger the mesh, the smaller the particle size. .

The particle size of the artificial silica sand is not limited in the present invention, it can be appropriately adjusted according to the requirements of the company or the product to be applied.

For example, when applying to a mold mold, the particle size is adjusted according to the type of raw material, that is, gray cast iron, malleable cast iron, impression graphite steel, cast steel or non-ferrous cast. In addition, it can be produced in the appropriate particle size according to the application, casting, cast steel, insulation, artificial marble, road aggregate, interior and exterior wall materials, floor mortar plastering, and waterproofing.

This particle size can be adjusted by controlling the type of grinder, the number of grinding, the rotation speed and the like in the artificial silica manufacturing process. Preferably, 12 to 18 mesh (1.7 to 1.0 mm), 20 to 40 mesh (0.85 to 0.42 mm), 40 to 70 mesh (0.42 to 0.22 mm), and 70, considering the particle size of natural silica sand commercially available Standard production is possible with sizes of from 200 mesh (0.22 to 0.1 mm).

In addition, the artificial silica according to the present invention has a dry shrinkage rate of +0.40 to + 0.80% expansion and plastic shrinkage rate of +1.2 to + 3.5% expansion.

The dry shrinkage was calculated by comparing the length before drying after the artificial silica sand was dried for 3 hours at 110 ℃ for the test drying, and the meaning of '+' indicates that the dry shrinkage was expanded. The smaller this means, the higher the dimensional stability of the product obtained by using the artificial silica sand.

In the case of the artificial silica sand according to the present invention, the dry shrinkage rate is less than + 0.80%, preferably +0.40 to + 0.80%, more preferably +0.44 to + 0.74% shows a result almost similar to the natural silica sand commonly used.

The firing shrinkage was calculated by measuring the change in length after firing at 1290 ° C. for 180 minutes and comparing with the length before firing. The meaning of '+' indicates that the firing shrinkage was expanded by firing. Similarly, the dimensional stability of the product obtained by using artificial silica sand is high and the heat resistance is excellent, which means that no cracking or cracking of the product occurs.

In the case of the artificial silica sand according to the present invention, the plastic shrinkage rate is less than + 3.5%, preferably +1.2 to + 3.5%, more preferably +1.38 to + 2.56%. This is very low compared with the plastic shrinkage rate of about + 11.0% of commercially available natural silica sand, which means that it suppresses the volume change of SiO ₂ by controlling the content of Al ₂ O ₃ contained in artificial silica sand. do.

Artificial silica according to the present invention as described above is prepared by grinding and classifying the feldspar coating.

Conventional natural silica sand uses quartz or quartzite as a raw stone. However, in the present invention, a feldspar coating is used as a raw stone of artificial silica.

Pyrophyllite is a mineral that is formed by quartz hydrolysis, andesite, rhyolite, and tuff, and undergoes hydrothermal alteration.

The feldspar coating contains Al ₂ O ₃ , SiO ₂ , K ₂ O and other impurities, and is commonly used 10 to 18% by weight of Al ₂ O ₃ , 74 to 85% by weight of SiO ₂ , and 2 Gemstones containing -6% by weight of K ₂ O and other impurities are possible. The impurities include Fe ₂ O ₃ , CaO, MgO, K ₂ O, and Na ₂ O, from 0.1 to 1.0 wt% Fe ₂ O ₃ , from 0.2 to 0.5 wt% CaO, from 0.05 to 0.2 wt% MgO, and It contains 0.1 to 1.0% by weight of Na ₂ O.
These feldspar pottery is not melted at 1300 ~ 1700 ℃ and has a low expansion rate than other Australian, Vietnamese, Chinese natural silica sand has a high fire resistance to withstand high thermal changes.

The grinding of the gemstones is carried out several times to have the same spherical particle form as natural silica sand.

As is known, pulverization is a unit operation that obtains finer powder by pulverizing a solid raw material mainly by a mechanical method. It is an operation that consumes a large amount of energy, and according to various factors-the type of pulverization device, pulverization speed, operation method, etc. Grinding efficiency depends.

Therefore, in order to produce a spherical particle shape and a desired size of artificial silica sand with high efficiency, the sorting of a pulverizing device, an operation method and the order thereof are important.

1 is a flow chart showing a manufacturing method of artificial silica sand according to an embodiment of the present invention.

Referring to FIG. 1, first, the selected feldspar stone is inputted using a conveyor belt.

Subsequently, the gemstones are put into the first grinder 10 capable of digesting an amount of work of about 30 to 50 tons per hour, and the size of the gemstones is pulverized to 100 to 150 mm or less.

Next, using the conveyor belt, the raw material pulverized to 100 to 150 mm or less is introduced into a second crusher 20 capable of extinguishing a work load of about 20 to 30 tons per hour, so that the size is 50 to 70 mm. Crush.

In this case, it is preferable to use a grinder (or a crusher) as the first grinder 10 and the second grinder 20.

The grinder is used to grind several tens of cm of raw material into tens of centimeters of large particles, and is primarily used for crushing rocks or ores in blasted or rough state. The crusher may be a gyro crusher, jaw crusher, Laura crusher, cone crusher, or the like.

Preferably, a jaw crusher (Jaw Crusher) is used as the first crusher 10, and the second crusher 20 uses a jaw crusher secondary crusher to crush into smaller particles. Such jaw crusher crushing occurs by compression between two jaw-shaped crushing plates, and is used for preliminary crushing of ore.

Next, the raw stone powder pulverized to 50 to 70 mm or less is introduced into a third crusher 30 capable of extinguishing a work load of about 30 tons per hour, and pulverized so as to have a size of 0.1 to 30 mm. do.

The third grinder 30 uses a cone crusher (Cone Crusher) to grind the raw stone powder passed through the second grinder 20 into smaller particles. The crusher grinder grinds and grinds by rotation without rotating the independent cone, and allows grinding to a smaller particle size.

Next, the powder pulverized to 0.1 to 30 mm or less using a conveyor belt is introduced into a fourth crusher 40 capable of extinguishing an amount of work of about 8 to 10 tons per hour, so that the size is 0.1 to 3.0 mm. Crush.

The fourth grinder 40 is preferably a hammer crusher grinder. Since the hammer crusher is pulverized while rotating at a high speed in the shape of a hammer, the crusher can be pulverized so that the particle shape is not sharp but close to an oval using such a hammer crusher.

Next, the powder pulverized to 0.1 to 3.0 mm or less is separated into particle sizes by the particle size separator 50, and then 3.0 mm or less is transferred to the fifth grinder 60 using a conveyor belt, and 3.0 mm or more is transferred to the fourth grinder 60. It is returned to 40 and regrind so that the particle size of the powder is 3.0 mm or less.

The particle size separation may be a commonly used mesh separator, and the size of the final obtained particles is controlled through this conveyance.

Next, the powder pulverized to 0.1 to 3.0 mm using a conveyor belt is put into a fifth crusher 60 capable of extinguishing a work load of about 4 to 6 tons per hour, and pulverized to have a size of 0.1 to 2.0 mm. To form the same shape as the granular natural silica sand.

At this time, it is preferable that the fifth grinder 60 also uses a hammer crusher grinder. At this time, the hammer crusher crusher is pulverized by repetition of the impact of the vertical rise and fall of the hammer, and pulverizes the form of artificial silica sand close to the spherical shape.

After the pulverization process of the above-described several stages, the pulverized powder is transferred to the particle size separator to separate each particle size.

The particle size separator 70 may be commonly used, and for example, the artificial silica is separated into 8 to 12 mesh, 12 to 18 mesh, 20 to 40 mesh, and 40 to 70 mesh.

The isolated artificial silica is packaged according to the product size and is provided to the consumer as an example of 1 ton P.P bag.

Artificial silica obtained through these steps is a high content of Al ₂ O ₃ components in the composition compared to natural silica sand can be applied to all fields where conventional natural silica sand is applied. Preferably, the glass industry and casting industry, such as plate glass and glass products, other steelmaking, steelmaking, cement, sodium silicate, chemical industry filler, refractory brick manufacturing, tiles, sanitary ware, household ceramics, electric insulators, electrical insulation and thermal insulation, cold storage It is used as a raw material of glass fiber which requires such characteristics.

Particularly, when applied to the mold mold, the Al ₂ O ₃ component in the composition is contained in a higher content than natural silica sand, thereby preventing cracking or cracking of the mold mold, which has occurred during the use of natural silica sand.

Hereinafter, the present invention will be described in more detail based on the following examples, but the present invention is not limited to the examples.

EXAMPLE

(Example 1)

Pyrophyllite ore is charged into a jaw crusher (capacity 150-250 HP, 30-50 tons / hour) and firstly pulverized to 150 mm or less, and into a jaw crusher (capacity 75 HP, 20-30 tons / hour). It was added and crushed secondly to 70 mm or less, and then put into a Koncrusher grinder (capacity 150 HP, 30 tons / hour) and tertiarily crushed to 30 mm or less. Subsequently, the obtained powder was crushed qualitatively to 3.0 mm with a hammer crusher grinder (volume 75 HP, 8 to 10 tons / hour), and the powder of 3.0 mm or more was again crushed to a hammer crusher grinder (volume 75 HP, 8 to 10 tons / hour). Pulverized), and then again pulverized up to 2.0 mm or less with a hammermer crusher (capacity 100 HP, 4-6 tons / hour). By separating the obtained powder with a particle size separator, 8 to 12 mesh (No. 3: 2.36 to 1.70 mm) 12 to 18 mesh (No. 4: 1.70 to 0.96 mm), 20 to 40 mesh (No. 5: 0.85 to 0.42 mm), 40-70 mesh (No. 6: 0.42-0.22 mm) of artificial silica sand was produced, respectively.

Experimental Example 1 Particle Size Analysis

The artificial silica obtained in Example 1 was measured by a particle size analyzer, and the obtained results are shown in FIGS. 2 to 5. % Is weight%.

Fig. 2 is a graph of particle size analysis of 8 to 12 mesh yarn No. 3, 87% of artificial silica of 18 mesh, 10.5% of artificial silica of 20 mesh, 1.4% of artificial silica of 30 mesh, and artificial mesh of 40 mesh. Represents 1.1%, indicating that the particle size has a relatively narrow distribution.

3 is a particle size analysis graph of 4 to 4 artificial yarn of 12 to 18 mesh, 2.8% artificial silica of 18 mesh, 39% of artificial silica of 20 mesh, 42% of artificial silica of 30 mesh, 40 mesh of artificial silica It is found that 14.2% of the artificial silica of 1.0%, 50% of artificial mesh of 0.5 mesh, 0.5% of artificial silica of 0.5 mesh, 0.3% of artificial silica of 100 mesh and 0.2% of artificial silica of 100 mesh.

Figure 4 is a particle size analysis graph of 5 to 40 artificial yarn of 20 to 40 mesh, 0.5% of artificial silica of 18 mesh, 3.5% of artificial silica of 20 mesh, 31.4% of artificial silica of 30 mesh, 40 mesh of artificial silica 52%, 50 mesh artificial silica, 9.8%, 70 mesh artificial silica 1.5%, 100 mesh artificial silica 0.7%, 140 mesh artificial silica 0.6%.

Figure 5 is a particle size analysis graph of No. 6 artificial silica of 40 to 70 mesh, 0.2% artificial fiber of 30 mesh, 12% of artificial silica of 40 mesh, 46% of artificial silica of 50 mesh, artificial silica of 70 mesh It can be seen that 41%, 100 mesh artificial silica sand 0.5%, 140 mesh artificial silica sand 0.3%.

Experimental Example 2 Composition Analysis

The chemical composition of the artificial silica obtained in Example 1 was compared with the conventional commercial silica using EDS analyzer (Energy Dispersive x-ray Spectroscopy, elemental analysis device).

Content (% by weight) SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ CaO MgO K ₂ O Na ₂ O Artificial silica of Example 1 78.0 14.5 0.5 0.4 0.1 4.0 0.5 Australian natural silica 99.6 0.02 0.003 - - - - Vietnamese natural silica 99.5 0.03 0.002 - - - - Chinese natural silica sand 87-95 1.5 to 2.2 1.7 to 2.5 - - 2 to 4 - Jumunjin Natural Silica 75 to 87 2.3 2.1 to 2.5 - - 5 to 7 -

Referring to Example 1, it can be seen that the artificial silica obtained in accordance with the present invention has a high content of alumina component.

Experimental Example 3 Thermal Expansion Rate Analysis

The coefficient of thermal expansion according to the temperature of the artificial silica sand and commercial natural silica sand of Example 1 is measured and shown in Table 2 below.

250 ℃ 450 ℃ 650 ℃ 800 ℃ 1000 ℃ Artificial silica of Example 1 0.154 0.359 0.662 0.73 0.78 Australian natural silica 1.480 0.973 2.57 3.2 7.2 Vietnamese natural silica 0.507 1.1 2.6 3.3 7.2 Chinese natural silica sand 0.53 1.2 2.7 3.7 8.1 Jumunjin Natural Silica 0.43 1.0 2.43 3.1 4.7

Referring to Table 2, the artificial silica of Example 1 prepared according to the present invention showed a low thermal expansion rate compared to other natural silica sand.

Furthermore, looking at the degree of thermal expansion according to the temperature at 250 ℃ to 1000 ℃, it can be seen that about 5 times increased in the case of artificial silica sand of Example 1, but increases up to 10 times or more in the case of conventional commercial silica.

This result means that when the artificial silica sand according to the present invention is used in the mold mold, the volume change according to the temperature is low, thereby preventing cracking or cracking.

Experimental Example 4 Physical Property Analysis

The physical properties of artificial silica sand obtained in Example 1 and commercially available natural silica sand were measured and shown in Table 3 below.

At this time, the drying shrinkage rate was calculated by comparing the length before drying by measuring the change in length after drying for 3 hours at 110 ℃ by drying the artificial silica sand in a container. The plastic shrinkage rate was calculated by measuring the change in length after firing artificial silica sand at 1250 ° C. for 3 hours and comparing it with the length before firing. In addition, the loss of ignition (Ig loss, ignition loss) was calculated by measuring the difference between the weight after the drying and the weight after the baking and compared with the weight after drying it to calculate the burning loss.

Content (% by weight) Dry Shrinkage (%) Plastic Shrinkage (%) Burn loss (%) Melting Point (℃)  Artificial silica of Example 1 No. 3 +0.44 +1.38 +1.75 1670 ℃ No. 4 +0.64 +1.5 +3.0 1670 ℃ No. 5 +0.64 +1.5 +2.9 1670 ℃ No. 6 +0.74 +2.56 +4.0 1670 ℃ Australian natural silica +0.54 +11.7 +0.2 1730 ℃ Vietnamese natural silica +0.32 +11.5 +0.2 1730 ℃ Chinese natural silica sand +0.42 +10.5 +0.5 1690 ℃ Jumunjin Natural Silica +0.34 +7.6 +0.7 1560 ℃ No. 3 yarn: 8 to 12 mesh (2.36 to 1.70 mm) No. 4 yarn: 12 to 18 mesh (1.70 to 0.96 mm) No. 5 yarn: 20 to 40 mesh (0.85 to 0.42 mm) No. 6: 40 to 70 mesh (0.42 to 0.22) mm) 7 yarn: 70 to 200 mesh (0.22 to 0.075 mm)

Looking at Table 3, the artificial silica obtained according to the present invention can be seen that the degree of expansion during the plastic shrinkage test is very low compared to the natural silica sand, high fire resistance and excellent quality.

In particular, natural silica sand has a very high degree of expansion during plastic shrinkage test, which is caused by volume change as SiO ₂ causes crystal phase transition at a high temperature.

In comparison, the artificial silica sand according to the present invention has a low expansion ratio at high temperatures compared to other natural silica sand, and thus it can be seen that there is no crack or other abnormality of the mold when used as a casting sand, thereby enabling the production of a stable product.

( Experimental Example  5) Particle Morphology Analysis

The grain shape of the artificial silica sand obtained in Example 1 and commercially available natural silica sand was measured under a microscope, and the obtained results are shown in FIGS. 5A to 9.

Figure 6a is a micrograph showing the particle form of artificial silica sand obtained in Example 1, Figure 6b is an enlarged photograph of the Figure 6a, Figure 7 is a micrograph showing the particle shape of Australian natural silica sand, Figure 8 is made in Vietnam It is a micrograph showing the particle shape of natural silica sand, Figure 9 is a micrograph showing the particle shape of natural silica of Chinese natural silica, Figure 10 is a micrograph showing the particle shape of jumjin acid natural silica sand.

6A to 10, it can be seen that the granular sand grains obtained according to the present invention have a shape similar to that of commercially available natural silica sand (see FIGS. 7 to 10).

As described above, the artificial silica sand having improved heat resistance with a high Al ₂ O ₃ content compared to natural silica sand was prepared using the feldspar pottery as a starting material. The artificial silica sand can be used as a substitute for natural silica sand, and when applied to the mold mold to eliminate the cracking and cracking of the mold mold generated during the work of the casting process.

Claims (11)

delete delete delete delete delete Grind and classify the feldspar coating containing 10-18% by weight of Al ₂ O ₃ , 74-85% by weight SiO ₂ , and 2-6% by weight of K ₂ O, and the balance with other impurities, The milling is first milled to 100 to 150 mm, second milled to 50 to 70 mm, third milled to 0.1 to 30 mm, fourth milled to 0.1 to 3.0 mm, and fifth ordered to 0.1 to 2.0 mm. Through the grinding process, SiO ₂ 74-85 wt%, Al ₂ O ₃ 10-18 wt%, Fe ₂ O ₃ 0.1-1.0 wt%, CaO 0.2-0.5 wt%, MgO 0.05-0.2 wt%, K ₂ O 2-6 wt% And, and a method for producing artificial silica, characterized in that the artificial silica comprising 0.1 to 1.0% by weight of Na ₂ O. The method of claim 6, 3.0 mm or more of the powder after the fourth crushing method for producing artificial silica, characterized in that for performing a further step of regrinding. The method of claim 6, The first and second milling is carried out with a jaw crusher grinder, the third crushing is carried out with a cone crusher grinder, and the fourth and fifth milling is performed by a hammer crusher grinder. delete delete delete

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